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1.
提出了一种基于小波变换的管理数据处理方法,把公司管理上的数据看成一个非平稳的时间序列,利用小渡函数将该时间序列分解到不同的频率通道上,然后将分解后的信号当作近似的平稳时间序列,用一些传统的统计方法进行预测,同时对中国足球彩票若干期的销售量数据进行了处理和预测,并将结果与实际销量以及用传统的AR模型的预测值进行了比较。 相似文献
2.
Olive Oil Consumption in Greece: A Microeconometric Analysis 总被引:2,自引:1,他引:1
Panagiotis Lazaridis 《Journal of Family and Economic Issues》2004,25(3):411-430
In this paper, the factors affecting at-home demand for three types of oils and fats in Greece, with emphasis on olive oil, are investigated using the linear approximation of the Almost Ideal Demand System and family budget survey data. To overcome the econometric problem created with the existence of zero expenditure, a generalization of the two-stage Heckman procedure is employed. In order to investigate the role of self-consumption, two different samples were used. The first includes all households; the second excludes those that acquire olive oil only from own production. According to the results, there are important differences in the first stage of the decision process between the two samples. Unlike the first stage, the second stage of the decision process found no important differences between the results for the two samples. 相似文献
3.
Craig H. Mallinckrodt Christopher J. Kaiser John G. Watkin Michael J. Detke Geert Molenberghs Raymond J. Carroll 《Pharmaceutical statistics》2004,3(3):171-186
The last observation carried forward (LOCF) approach is commonly utilized to handle missing values in the primary analysis of clinical trials. However, recent evidence suggests that likelihood‐based analyses developed under the missing at random (MAR) framework are sensible alternatives. The objective of this study was to assess the Type I error rates from a likelihood‐based MAR approach – mixed‐model repeated measures (MMRM) – compared with LOCF when estimating treatment contrasts for mean change from baseline to endpoint (Δ). Data emulating neuropsychiatric clinical trials were simulated in a 4 × 4 factorial arrangement of scenarios, using four patterns of mean changes over time and four strategies for deleting data to generate subject dropout via an MAR mechanism. In data with no dropout, estimates of Δ and SEΔ from MMRM and LOCF were identical. In data with dropout, the Type I error rates (averaged across all scenarios) for MMRM and LOCF were 5.49% and 16.76%, respectively. In 11 of the 16 scenarios, the Type I error rate from MMRM was at least 1.00% closer to the expected rate of 5.00% than the corresponding rate from LOCF. In no scenario did LOCF yield a Type I error rate that was at least 1.00% closer to the expected rate than the corresponding rate from MMRM. The average estimate of SEΔ from MMRM was greater in data with dropout than in complete data, whereas the average estimate of SEΔ from LOCF was smaller in data with dropout than in complete data, suggesting that standard errors from MMRM better reflected the uncertainty in the data. The results from this investigation support those from previous studies, which found that MMRM provided reasonable control of Type I error even in the presence of MNAR missingness. No universally best approach to analysis of longitudinal data exists. However, likelihood‐based MAR approaches have been shown to perform well in a variety of situations and are a sensible alternative to the LOCF approach. MNAR methods can be used within a sensitivity analysis framework to test the potential presence and impact of MNAR data, thereby assessing robustness of results from an MAR method. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
张红伟 《江苏大学学报(高教研究版)》2008,(4):81-84
当下大学生的权利被广泛关注,但是大学生的权利却往往不能得到很好的保障和维护,其中一个重要原因就是大学生缺乏一个强有力的权力保障。在我国高等教育的现实中,大学生在学校管理中的权力却微乎其微。权利必须用权力来维护和保障。由此,应正视权利和权力的本质区别;在学校管理中赋予大学生合法的地位和身份,给予其参与管理学校的权力;组建大学生自治组织,用相对独立的权力维护其权利,从而加强大学生在学校管理中的权力来使大学生权利得到根本性的保障和维护。 相似文献
5.
Pierre Legendre François-Joseph Lapointe 《Australian & New Zealand Journal of Statistics》2004,46(4):615-629
A test of congruence among distance matrices is described. It tests the hypothesis that several matrices, containing different types of variables about the same objects, are congruent with one another, so they can be used jointly in statistical analysis. Raw data tables are turned into similarity or distance matrices prior to testing; they can then be compared to data that naturally come in the form of distance matrices. The proposed test can be seen as a generalization of the Mantel test of matrix correspondence to any number of distance matrices. This paper shows that the new test has the correct rate of Type I error and good power. Power increases as the number of objects and the number of congruent data matrices increase; power is higher when the total number of matrices in the study is smaller. To illustrate the method, the proposed test is used to test the hypothesis that matrices representing different types of organoleptic variables (colour, nose, body, palate and finish) in single‐malt Scotch whiskies are congruent. 相似文献
6.
Maximum likelihood estimation and goodness-of-fit techniques are used within a competing risks framework to obtain maximum likelihood estimates of hazard, density, and survivor functions for randomly right-censored variables. Goodness-of- fit techniques are used to fit distributions to the crude lifetimes, which are used to obtain an estimate of the hazard function, which, in turn, is used to construct the survivor and density functions of the net lifetime of the variable of interest. If only one of the crude lifetimes can be adequately characterized by a parametric model, then semi-parametric estimates may be obtained using a maximum likelihood estimate of one crude lifetime and the empirical distribution function of the other. Simulation studies show that the survivor function estimates from crude lifetimes compare favourably with those given by the product-limit estimator when crude lifetimes are chosen correctly. Other advantages are discussed. 相似文献
7.
费艳颖 《大连理工大学学报(社会科学版)》2007,28(1):88-92
专利权的地域性是专利权法律冲突肯定说和否定说争议的焦点所在.文章通过分析专利权地域性的成因暨合理性,指出无论是国内法还是国际公约,适时地突破专利权地域性均不存在制度上的障碍.认为地域性并不是专利权的本质属性;随着各国政治、经济、文化环境的优化,专利权地域性的消失带有必然性;各国在处理涉外的专利权合同关系和侵权关系时,应突破地域性理论的窠臼,建立适宜的法律适用规则以解决存在的法律冲突. 相似文献
8.
Cédric Béguin Beat Hulliger 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2004,167(2):275-294
Summary. As a part of the EUREDIT project new methods to detect multivariate outliers in incomplete survey data have been developed. These methods are the first to work with sampling weights and to be able to cope with missing values. Two of these methods are presented here. The epidemic algorithm simulates the propagation of a disease through a population and uses extreme infection times to find outlying observations. Transformed rank correlations are robust estimates of the centre and the scatter of the data. They use a geometric transformation that is based on the rank correlation matrix. The estimates are used to define a Mahalanobis distance that reveals outliers. The two methods are applied to a small data set and to one of the evaluation data sets of the EUREDIT project. 相似文献
9.
张敏 《合肥工业大学学报(社会科学版)》2008,22(1):53-57
经济转轨的基础决定了中国与俄罗斯的经济转轨方向的不同,产权改革的效率决定两国经济转轨的成效。通过两国经济转轨的比较,文章认为有三个方面的深刻经验教训特别值得我们重视,即经济转轨必须高度重视政府的作用、产权私有化并非提高效率的充分必要条件、产权制度的变迁具有演进性和不可复制性。 相似文献
10.
Backfitting Random Varying-Coefficient Models with Time-Dependent Smoothing Covariates 总被引:1,自引:0,他引:1
Abstract. In this paper, we propose a random varying-coefficient model for longitudinal data. This model is different from the standard varying-coefficient model in the sense that the time-varying coefficients are assumed to be subject-specific, and can be considered as realizations of stochastic processes. This modelling strategy allows us to employ powerful mixed-effects modelling techniques to efficiently incorporate the within-subject and between-subject variations in the estimators of time-varying coefficients. Thus, the subject-specific feature of longitudinal data is effectively considered in the proposed model. A backfitting algorithm is proposed to estimate the coefficient functions. Simulation studies show that the proposed estimation methods are more efficient in finite-sample performance compared with the standard local least squares method. An application to an AIDS clinical study is presented to illustrate the proposed methodologies. 相似文献